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Higher Mileage during Summer Months?

Discussion in 'Gen 2 Prius Main Forum' started by airpolgas, Jun 5, 2006.

  1. airpolgas

    airpolgas New Member

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    It's been said that mileage increases as the temperature increases. My question is how?

    On a 70 degree day, I have my windows closed, with the air circulating inside. I can normally go about the entire trip with this setup.

    On a 75 degree day, the temperature inside the car goes up considerably that I either have to crack the windows open or turn the AC on (setting it to 72 - LO fan or non Auto).

    How would you guys deal with increasing your mileage and being comfortable at the same time this summer months?

    We had a 97-106 degree last weekend, and I went from 48 MPG to 44.3 (my lowest so far) within two hours because of the AC in full blast.
     
    #1 airpolgas, Jun 5, 2006
  2. richard schumacher

    richard schumacher shortbus driver

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    In Dallas: keep the windows up, the A/C cranked on recirculate, and, if necessary, drive a little more gently.
     
    #2 richard schumacher, Jun 5, 2006
  3. Tideland Prius

    Tideland Prius Moderator of the North
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    Depends where we are. It doesn't get too hot where I live so I can maximise my summer mileage, although I'm not at 60mpg levels because of hills here. 20-25°C is the norm, occasionally pushing 28-30 (by the water that is) around Jul/Aug so my A/C usually isn't at full blast.

    I would maximise the use of a sunshade. That black dashboard really soaks up the heat and once you out and in the sun, you'll have to use more A/C to keep the interior cool.

    You could also try tinting your windows if gets really hot for several months where you are.

    Short trips kill mileage. Short trips and A/C drains it. I'd suggest turning the A/C off and opening the windows 5 mins before you plan to park the car or at least enjoy the cool air until it warms up, then wind the windows down if you haven't parked yet. This way, you don't have the car cooling the interior (residue cooling that is) when no one's inside.

    Of course, wind the windows down if it's hot inside and blow the hot air out. It's much more effective than trying to cool that hot air.

    Run the A/C at the highest possible temperature that keeps you comfortable. Running it at MAX COLD drains the battery. I know, cause just my luck, a train was crossing and I had to wait. I've never seen my battery go from 5 bars to 2 bars (then engine on) so quickly.
     
    #3 Tideland Prius, Jun 5, 2006
  4. Powder

    Powder New Member

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    To my understanding, it's because high temperature means lower air density, which also means there's less drag, thus less fuel burned. Usually you can only see the savings when the temperature between cold day and hot day is drastic.

    It's more beneficial to drive with A/C on than having your windows open because the open windows drastically increase the drag and end up causing more fuel to be used.
     
    #4 Powder, Jun 5, 2006
  5. HTMLSpinnr

    HTMLSpinnr Super Moderator
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    I know increased A/C usage will tax mileage. Today, it was 100-104°F outside on my way to work. I filled up 6 miles into my trip (car was warmed up), and then I used cruise control at 65mph (with one burst to 70, and ~1 mile at 55mph) along with 1 mile of city driving to work. This yielded 60.3mpg for the trip.

    [attachmentid=3701]

    I imagine if it was more like 110-113°F like I saw Saturday, the MPG would have been lower due to higher A/C usage. For reference, my A/C is set to auto at 78°F, and I have 59k miles on my car.

    Note, my first 5 minutes (not shown) prior to fillup was probably 30mpg tops, and outside temp at the time was 90-93°F
     
    #5 HTMLSpinnr, Jun 5, 2006
  6. Brian K

    Brian K New Member

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    In warm weather you can use regenerated juice to run the A/C if you need it, in the winter the ICE absolutely MUST run to get heat. We notice better mileage when the temperature warms into the high 50s to low 60s.

    There is probably a second factor. As the temperature dips greases and oils thicken, it takes additional power to get things to move when the lube thickens. I know that's a factor for us here in Maine at -20 and lower, maybe not for other folks. Heck, at those temperatures it almost feels like the brake is on even though you know it's off, but one can feel the drag of the thick lube.
     
    #6 Brian K, Jun 5, 2006
  7. airpolgas

    airpolgas New Member

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    I just got back from an hour of driving, and I have to say, I never thought 78 would be comfortable. Thanks for this tip, I'll now set my AC on 78 for those very hot summer days.
     
    #7 airpolgas, Jun 5, 2006
  8. EricGo

    EricGo New Member

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    I live in a very low humidity and hot climate in the summer. (NOT AZ -- just hot in the 90 - 105F range).

    1. Tint is great. I have llumar atr 20 that rejects about 50% of the hear, and 80% visible ligt. Hot in the shade is *much* more tolerable than hot in the sun.

    2. I use a front window shade every chance I have, and crack the windows open when the car is sitting. As an aside, I also keep the hatch compartment covered, to protect the HV.

    3. I drive the first ~ 5 minutes with all windows about 1/3 down to air out the car, while still gaining some shade from the tint. If I am driving low speeds less than 40 mph and the heat is bearable, I leave the AC off and windows cracked about 2 inches all around. If I am driving faster, or still too hot, windows go up, and I set AC at 80F, high(er) fan, recirculate air. If I am the only driver, this is quite pleasant; if I have to direct the fans up to air out the back passengers it is warm but ok.

    Overall this is good for low 60's mpg, compared to high 60's when the weather is ideal.
     
    #8 EricGo, Jun 5, 2006
  9. Jack Straw

    Jack Straw New Member

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    zzz
     
    #9 Jack Straw, Jun 5, 2006
  10. airpolgas

    airpolgas New Member

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    <div class='quotetop'>QUOTE(EricGo @ Jun 5 2006, 06:22 PM) [snapback]266362[/snapback]</div>
    Damn, Eric, you get low 60's on a bad day. I have had the car since december, and my best tank is 50.2 :angry:
     
    #10 airpolgas, Jun 5, 2006
  11. EricGo

    EricGo New Member

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    <div class='quotetop'>QUOTE(airpolgas @ Jun 5 2006, 11:48 PM) [snapback]266466[/snapback]</div>
    If you like, I'll quote you some numbers when my wife goes out for short trips in the winter ;)
    That will make you feel *much* better.
     
    #11 EricGo, Jun 6, 2006
  12. BVISAILMAN

    BVISAILMAN Junior Member

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    I have founf that using the AC on lower speeds has virtually NO effect on my mileage. So when I first get in the car I use AC/auto, set the temp and as soon as I start to feel comfy, I put the AC on a lower fan speed. Remember the AC is running off Electricity not a pully from the engine. My experience so far in over 4000 miles on my 2006 is that any difference in MPG is negligable. I am averaging (overall since delivery) 50.5 MPG. with about 40% city and 60% highway driving
     
    #12 BVISAILMAN, Jun 6, 2006
  13. Vegas Prius&#33;

    Vegas Prius&#33; New Member

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    What realy beats me up is stop-n-go traffic with the air on. It has been >105 here for the last week, and sitting at a stop light with the AC on (set about 76 or so) just drains the battery very fast, then my mileage suffers a lot until a good long stretch when it charges back up. Causes me to get 45-47 MPG. Was holding a fairly steady 50.
     
    #13 Vegas Prius&#33;, Jun 6, 2006
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